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In the general population, depression is exceedingly common, sometimes difficult to diagnose, and undertreated but remediable [1, 2]. In patients with chronic conditions such as diabetes, depressive disorders seem to occur even more frequently [3], have a high rate of recurrence [4], and seem to be associated with worsened medical outcomes [5]. The high prevalence of depression in diabetes [3], the frequency of depression onset before diabetes complications [6, 7], the similarity in the hypothalamic-pituitary axis changes found in depression and poorly controlled diabetes mellitus [8], indications that diabetic rats are more susceptible to neurochemical and behavioral changes similar to those found in depression [9], and mood shifts often associated with glycemic changes [10] all raise interesting questions about the direction of causality and biological mechanisms linking depression and diabetes. However, there is very little evidence to provide clear guidance on either issue.